This invention relates generally to image guided surgery. More specifically, the present invention relates to a method and system which facilitates use of pre-acquired images of an anatomical body to pre-plan and perform medical procedures.
In recent years, image guided surgery has become more and more common, in part because of the ability of a surgeon to view internal images of a patient""s anatomy and pre-plan a medical operation. In this way, pre-acquired images of the anatomical body are used to plan the course of the medical procedure, whether the medical procedure is diagnostic, therapeutic or surgical in nature. The pre-acquired images can also be used, to some extent, during the medical procedure for orientation of the surgeon with respect to the internal anatomy of the patient.
The images of a patient""s external or internal anatomy used in image guided surgery can be generated by a number of means, including computerized tomography (CT), magnetic resonance imaging (MRI), video, ultrasound and X-rays. Images may also be captured using angiography, single photon emission computer tomography and positron emission tomography (PET). In all cases, at least two, and generally more than two, images of the patient""s internal anatomy are generated. The images are captured such that the relative position of the images is known. The images, along with information indicating the relative position of the images, can then be stored in a data-base to essentially create a data-base body comprised of the pre-acquired images and corresponding to the anatomical body of the patient at the time the images were captured.
This data-base body of images can be used for a number of purposes, including diagnosis or to pre-plan the medical procedure. In addition, it is known in the art to process this data-base body of pre-acquired images in order to produce images of various views, as well as three-dimensional images, based on the relative spatial relationship of the pre-acquired images within the internal anatomical structure of the patient.
Surgeons can pre-plan the course of a medical procedure by marking, either manually or electronically, on the data-base body of pre-acquired images the course of the medical procedure. The markings can indicate areas of interest, objects of concern, as well as proposed cuts or drilling locations and orientations, and locations which must be irradiated with specific types of radiation for diagnostic or therapeutic procedures. During the medical procedure, the surgeon can then refer to the markings on the images to assist in performing the procedure.
Furthermore, the prior art imaging devices can project a representation of the instrument or tool being used by the surgeon onto the pre-acquired images during a medical procedure. The representation corresponds to the position of the actual instrument or tool with respect to the patient. By viewing the position of the representation of the instrument or tool with respect to the data-base body of pre-acquired images, the surgeon can extrapolate the position of the actual probe or instrument with respect to the internal anatomy of the patient. In addition, the surgeon can simultaneously follow the pre-planned markings on the pre-acquired images.
However, the prior art imaging devices and methods suffer from the disadvantage that the surgeon""s attention is no longer directed solely toward the patient during the surgery, but rather is also directed toward the pre-acquired images, the pre-planned markings and the representations of the probes and instruments on the images. In other words, during image guided surgery, the surgeon""s attention is split between the patient and the data-base image of the patient. This is often disconcerting for surgeons, and in particular surgeons who are unfamiliar with image guided surgery, because their attention is no longer solely directed toward the patient, as is the case with other types of surgery. Rather, the surgeons must view the image of the patient and the representation of the probes and instruments with respect to the data-base image while manipulating the actual probes and instruments within the patient. This can adversely affect the surgeon""s hand-eye coordination and could result in the surgeon becoming disoriented.
Also, because the attention of surgeons during image guided surgery is split between the patient and the image of the patient, there is a risk that a surgeon will not notice that the surgeon has stuck, or will strike, a xe2x80x9ccritical structurexe2x80x9d within the patient. Critical structures include an organ or blood vessel, which, if struck, can critically or severely damage the patient. This is compounded by the fact that several imaging techniques do not provide detailed images of critical structures, such as organs or blood vessels, and a surgeon may not immediately see them if the surgeon""s attention is directed towards the pre-acquired images rather than at the patient.
A further disadvantage of the prior art imaging systems is that all pre-planned markings made by the surgeon are located on the pre-acquired images. Accordingly, in order to use the pre-planned markings, the surgeon must constantly refer to the images and orient the images and pre-planned markings to the anatomical body during the course of the medical procedure.
Accordingly, it is an object of this invention to at least partially overcome the disadvantages of the prior art. Also, it is an object of this invention to provide a method and system to facilitate image guided surgery by projecting onto the anatomical body during the medical procedure any markings made onto the data-base body of pre-acquired images.
Accordingly, in one of its aspects, this invention resides in a system for projecting onto an anatomical body markings made on a data-base body of pre-acquired images of the anatomical body, said system comprising: a spatial determinator for determining spatial positional information of the anatomical body in a frame of reference and generating first positional signals indicative of the spatial positional information of the anatomical body in the frame of reference; a mapping unit for receiving first positional signals indicative of the spatial positional information of the anatomical body in the frame of reference, mapping the markings made on the data-base body of pre-acquired images onto corresponding locations on the anatomical body and generating a mapping signal indicative of the corresponding locations in the frame of reference of the markings on the data-base body; and an image projecting device for receiving the mapping signal and projecting an image of the markings made on the data-base body onto the corresponding locations of the anatomical body.
In a still further aspect, the present invention provides a system for projecting onto an anatomical body markings made on a data-base body of pre-acquired images of the anatomical body, said system comprising: a spatial determinator for determining spatial positional information of the anatomical body by tracking the anatomical body in a frame of reference and generating first positional signals indicative of the spatial positional information of the anatomical body in the frame of reference; a mapping unit for receiving first positional signals indicative of the spatial positional information of the anatomical body in the frame of reference, mapping the markings made on the data-base body of pre-acquired images onto corresponding locations on the anatomical body and generating a mapping signal indicative of the corresponding locations in the frame of reference of the markings on the data-base body; and an image projecting device for receiving the mapping signal and projecting an image of the markings made on the data-base body onto the corresponding locations of the anatomical body, said image projecting device projecting the image substantially normal to a surface of a portion of the corresponding locations of the anatomical body.
In a further aspect, the present invention resides in a method for projecting onto an anatomical body markings made on a data-base body of pre-acquired images of the anatomical body, said method comprising the steps of: obtaining spatial positional information of the anatomical body in a frame of reference; mapping the markings made on the data-base body of pre-acquired images onto the corresponding locations on the anatomical body; and projecting an image of the markings made on the data-base body onto the corresponding locations of the anatomical body in the frame of reference.
In a further aspect, the present invention provides a method for projecting onto an anatomical body markings made on a data-base body of pre-acquired images of the anatomical body, said method comprising the steps of: obtaining spatial positional information of the anatomical body by tracking the anatomical body in a frame of reference; mapping the markings made on the data-base body of pre-acquired images onto corresponding locations on the anatomical body; and projecting an image of the markings made on the data-base body onto the corresponding locations on the anatomical body in the frame of reference substantially normal to a surface of a portion of the corresponding locations of the anatomical body.
One of the advantages of the present invention is that an image corresponding to the markings made by the surgeon onto the data-base body of pre-acquired images can be viewed during the surgical procedure directly on the patient. In other words, the surgeon will have the benefit of any markings made on the pre-acquired images during pre-planning of the medical procedure while the surgeon""s attention is directed to the patient. This permits the surgeon to more easily perform the medical procedure in a manner that the surgeon is accustomed to, rather than by watching the pre-acquired images and a representation of the instruments on the images.
A further advantage of the present invention is that the attention of the surgeon will be directed towards the patient for greater periods of time during the medical procedure. This will assist in the surgeon identifying critical structures, which may or may not have appeared in the pre-acquired images, before they are struck. Also, even if the critical structures have appeared on the pre-acquired images, the internal anatomy of the patient may have changed since the pre-acquired images were captured. For example, the internal organs or veins of a patient could have moved, either by movement of the patient, the actual incision by the surgeon, or other means. Clearly, these movements will not be reflected in the pre-acquired images as the movements occurred after the pre-acquired images were captured and the surgeon will only notice the changes by viewing the patient.
Another advantage of the present invention is that a surgical procedure can be planned by a surgeon located remote from the patient, and, with only the benefit of the pre-acquired images. For instance, the markings made on the pre-acquired images by the surgeon at the remote location will be projected onto the patient to assist the surgeon located proximate to the patient in performing the medical procedure. In addition, both surgeons can continue to mark the pre-acquired images in order to mutually identify the organs in the patient and the corresponding images of the organs in the pre-acquired images. In this way, telesurgery can be facilitated. Furthermore, in a preferred embodiment, the remote surgeon could initially mark portions of the anatomical body with a beam which is only visible to the remote surgeon and not visible to the local surgeon. For instance, the remote surgeon could mark the pre-acquired images to identify organs in the patient with an infrared laser. The infrared laser may be visible to a remote surgeon if the camera used by the remote surgeon can see infrared beams. However, the infrared beam would not be visible to the local surgeon. This may be advantageous by allowing the remote surgeon to take a moment and carefully draw and/or edit a region of interest entirely xe2x80x9cin privatexe2x80x9d before projecting an image to the local surgeon using visible light which the local surgeon can see. In this way, the local surgeon is not distracted while the remote surgeon becomes satisfied with the markings which one surgeon desires to show to the local surgeon. This technique can also be used for teaching purposes, or any other purpose in which the remote surgeon desires to mark specific areas which can only be seen by one surgeon and not the other surgeons.
Another advantage of the present invention is that the images projected by the image projecting device can be marked, either temporarily or permanently, onto the patient. This can be performed by having an image projecting device which emits radiation that can permanently mark a patient, such as by use of a CO2 laser which could mark the image onto the anatomy of the patient, either on the skin or on the bone. In a similar manner, use of an ultraviolet laser could be used to leave a mark on the skin of the patient corresponding to markings made to the pre-acquired images. Likewise, use of a photoreactive ink which perceptively changes in response to radiation emitted by the image projecting device can be used to temporarily mark the patient with markings made to the pre-acquired images. In a preferred embodiment, the photoreactive ink may be either thermochromic ink, which reacts to infrared radiation, or, photochromic ink which can react to different types of radiation, such as ultraviolet radiation. More preferably, the photoreactive ink may be embedded in a material, such as plastic, which is draped over the patient and then marked with the radiation emitted by the image projecting device, rather than applying the substance to the surface of the patient. In this way, the photoreactive ink embedded in the marking material would perceptively change and the image appear on the marking material, rather than the image appearing on a substance applied to the patient. In either case, a surgeon can quickly and accurately mark onto the patient any markings made onto the images during pre-planning, such that the markings will appear on the anatomical body after the image projecting device ceases projecting the image.
In another aspect of the present invention, the markings on the pre-acquired images can correspond to areas or tumors which must be irradiated as part of a photodynamic therapeutic procedure. In other words, substances which can change cells of the patient, such as photodynamic agents which react to specific types of radiation to become cytotoxic, can be applied to the patient. The image projecting device can be programmed to emit the types of radiation to which the photodynamic agent reacts. In this way, portions of the patient, such as tumors, can be eliminated or destroyed in a precise and predetermined manner by irradiating the patient with the specific type of radiation in a pre-planned manner. Also, because the radiation will be applied in a specific and pre-planned manner, a higher level of accuracy can be obtained for irradiating the patient, and therefore a more general photodynamic agent can be used which may be partially absorbed by the healthy tissue, as only the tumors will be irradiated. Likewise, a more intense beam of light can be used because it is less likely that healthy tissues will be irradiated.
Another advantage of the present invention is that the image projecting device can emit radiation to cauterize an area of the body. In this way, the area of the patient which is to be cauterized, such as the portion of the brain around a tumor that is to be removed, can be pre-planned and executed automatically once the tumor has been removed.
In a further embodiment, the image is projected substantially normal to a surface of the corresponding locations or a portion of the corresponding locations. In this way, by projecting the image substantially normal to a surface of the corresponding locations of the anatomical body, a clearer image is produced and optical distortions are reduced. Preferably, the image projecting device projects the image within 45 degrees of the normal of the surface where the corresponding locations are located. More preferably, the image projecting device projects the image within 30 degrees of the normal of the surface where the corresponding locations are located. If the corresponding locations extend over a large surface of the patient such that it is not possible to have a single image projecting device which can project an image substantially normal to the surface having the corresponding locations, the image projecting device may comprise more than one emitter such that different portions of the image will be projected by different emitters, each emitter projecting its portion of the image substantially normal to a part of the surface where the corresponding locations are located. In the event where two emitters are not practical, or, an entire image can still not be projected substantially normal to the entire surface where the corresponding locations are located, the portion of the image which is not substantially normal to a surface can be projected in a different manner, such as with dashed lines or in a different color, to bring to the attention of the surgeon that part of the image may contain optical distortion errors due in part to the image not being projected normal to the surface of the patient, or by surface features of the patient.
In a further embodiment, the image projecting device is then moved to a location which optimally projects the image onto the anatomical body. This position is generally determined to be a position whereby the projected beam is incident substantially normal to the surface upon which the image is being projected. Preferably, the incident angle is within 45 degrees, and more preferably 30 degrees, of the normal of the surface. To facilitate this, preferably the position and orientation of the image projecting device is tracked in the frame of reference. In this way, optical distortion errors have been found to be decreased, thereby improving their overall image projected by the image projecting device.
Further aspects of the invention will become apparent upon reading the following detailed description and drawings which illustrate the invention and preferred embodiments of the invention.